Removal of acetylene from diolefincontaining mixtures



Patented Oct. 12, 1948 REMOVAL OF ACETYLENE FROM DIOLEFIN- CONTAININGMIXTURES Egi V. Fasce, Baton Rouge, La., and William H.

Wood, Warren, Pa.; Sarah Thomas Fasce, at-

torney-in-fact for said Egi V. Fasce, assignors i to Standard OilDevelopment Company, a corporation of Delaware No Drawing. ApplicationNovember 30, 1944, Serial No. 565,839%

6 Claims. 1

This invention relates to improvements for the separation of acetylenesfrom hydrocarbon mixtures, and particularly to improvements for theseparation of acetylenes from hydrocarbon mixtures containing diolefinsand acetylenes,

The general method used for the separation of diolefins, particularlybutadiene, from hydrocarbon mixtures, such as those obtained by thermalcracking of a petroleum oil and by catalytic dehydrogenation of butenesand butanes, containing a high percentage of butadiene together' withother hydrocarbons such as acetylenes, is to contact the hydrocarbonmixture with ammoniacal cuprous acetate solution or other cuprous saltsolution in order to obtain as a product butadiene of extremely highpurity, but it has also been found that unsaturated hydrocarbons otherthan butadiene are also absorbed by the solutions when contactedtherewith. Since the copper solution has a high dissolving power foracetylenic compounds, such as methyl acetylene, ethyl acetylene, andvinyl acetylene, these hydrocarbons are undesirably removed along withthe diolefins. For instance, in the case of a hydrocarbon gas containing0.1% of any of the acetylenes designated, a copper solution brought toan equilibrium therewith at 100-F. contains about 0.19 mol of dissolvedacetylenes per liter of solution or about 0.8% by weight. Higherconcentrations of acetylene in the gas phase result in higherconcentrations of acetylene dissolved by the copper solutions. It is notdesirable to increase the dissolved acetylene content of these solutionsto too high a level as under such conditions polymerization andprecipitation of solid copper acetylides occur. The presence of theacetylides in an operating system is undesirable since they tend to stopthe flow of liquid and constitute a hazard due to their tendency todecompose with some violence. This explosive decomposition is greatlyincreased in the dry state and is always, therefore, a potential hazard.The presence of the polymers is particularly undesirable since they areexcellent emulsifying and foaming agents and cause plugging of thevarious pieces of equipment,particularly the absorption, stripping anddesorption towers. Consequently, it is desirable to first remove theacetylenes or at least reduce the concentration in the feed mixturebefore contacting with the copper solution.

According to this invention it has been found that the acetylenes may beselectively removed from the hydrocarbon mixture containing 'butadieneand acetylene by contacting the mixture with a catalyst comprising ametal of the iron 2 group, deposited upon certain types of carriers. Theimproved catalysts consist essentially of metallic nickel, cobalt oriron deposited upon highly active cracking catalysts such as acommercial sulfuric acid treated bentonite, aluminum silicate, syntheticimpregnated or plural gels of silica and alumina, silica and magnesia,or silica and alumina and magnesia, or acid-treated clays of thebentonitic and montmorillonitic type. The quantity of metal in thecatalyst may be between a 1 and by weight and is preferably betweenhours at a rate of 0.6 volume of oil per volume oi catalyst per hour at850 F. and substantially atmospheric pressure. The liquid products aresubjected to an Engler distillation up to 400 F. and the distillationand loss up to this tem perature is recorded as the D+L. A goodcrackingcatalyst is'one which gives a D+L yield greater than 25%. Theactive carriers to be used according to this invention, therefore, arethose which give D+L yields greater than 25%. For example such carriersas kieselguhr, pumice and the like are not suitable for this inventionsince they give D+L yields of only 8 to 12%.

The catalysts may be prepared'by impregnating the active carrier with asolution of a soluble salt of the metal, preferably the nitrate, thenextruding or otherwise shaping the plastic mass so obtained and dryingthe extruded mass in a steam oven at about 300 to 400", F. If thenitrate has been used for impregnation, some nitric acid as well asoxides of nitrogen will be evolved in this drying operation. Thereafterthe dried mass is heated in a furnace to a temperature between 500 and800 F. for a period of 10 to 12 hours or more in order to decompose theremaining nitrates. This results in a catalyst comprising the metaloxide deposited on the carrier. The metal oxide is then reduced to themetal by circulating hydrogen over the catalyst while the temperature isgradually raised to between about 600 and 900 F. This reductiontreatment may take place in the reaction vessel in which the catalyst isto be used and immediately following complete reduction thehydrogenation may be begun'by introducing the hydorcarbon feed. In somecases it is found that the activity of these catalysts 3 may beincreased still further by treating the metallic catalyst prepared inthe manner just described with sulfur-containing gases, such as hydrogensulfide, and then subsequently removing the sulfur by treatment withhydrogen.

The method oi preparing the improved catalysts will be better understoodfrom the following description 01' the preparation of 'a catalystcomprising about 7% metallic nickel on hydrofluoric acid-treatedbentonite: I

@bout 100 pounds oi an acid-treatedbentonite as obtained from themanufacturer is charged to a suitable mixing device, and about 100pounds of a 10% hydrofluoric acid solution is added thereto. The clayand solution are thoroughly mixed for a period of about an hour. A thinslurry is formed which is continuously charged to the top of a suitabledrying furnace. The inlet temperature of the furnace ,is maintained atabout 350 F. and the outlet temperature at about 600 F. The driedhydrofluoric acid-treated clay so obtained will still contain about 20%of volatile matter. It is then groundto a powder of about 200 mesh size.

fluoric acid-treated clay so obtained is charged to another mixingdevice which may be similar to the first one and about 4 gallons of asolution containing about 31 pounds of nickel nitrate, (N1(NO:)2.6H20)is added thereto. This quantity of nickel nitrate ,is equivalent toabout 8 pounds of nickel oxide or about 6.3 pounds of metallic nickel.The clay and solution of nickel nitrate are thoroughly mixed for about30 minutes and ordinarily a semi-plastic mass suitable for immediateextrusion will be obtained.-

If necessary, water may be added in sufllcient amounts to make themasssuitable for extrusion.

Too much water shouldnot be added because then a drying operation isrequired before ex-. trusion.

The plastic mass is extruded in any suitable means for this purpose andthe extruded massis dried in a steam oven for about 8 or 9 hours at atemperature of' about 325 F. The dried catalyst is then heated in afurnace to a temperature between 550 and 750 F. for a period of 12-h6urs to remove the last traces of nitrates.

The nickel oxide catalyst so obtained is placed,

in a suitable. pressure vessel adapted to withstandpressures of 3000pounds per square inch or more and hydrogen, free from sulfur and otherimpurities. is circulated through ,it-at a rate of about 1000 volumes ofgas per volume of catalyst per hour. The temperature ofthe catalyst israised at about 50 F. per hour to 325 F. and is maintained at this levelfor about 9 hours.- The temperature is,then raised further at about 30F. per hour to'450 F. Thereafter it is raised at 20 F. per hour to 550F. and at 10 F. per hour to about 600 F. or more and maintained at thislevel for about 24 hours. The catalyst is then ready' for use.

;The same general method of preparing the catalyst isapplicable when asynthetic impreg-v nated gel of silica and alumina is used as the baseinstead of an acid-treated bentonite. The synthetic impregnated gel may.be prepared in a number oi' diflerentways. which are known in the art,one convenient method being as follows: Equal portions of sodiumsilicate solution and acid are mixed in such concentrations as to form aclear, colloidal solution of silicic acid which upon standing sets intoa firm hydrogel structure.

The firm hydrogel after being permitted to set 7 40 only:

hydrogel so obtained isimpregnated with a solution of an aluminumcompound which can be decomposed or converted into aluminum oxide, forexample aluminum nitrate or aluminum acetate. The impregnated. hydrogelis dried and then slowly heated to a temperature of about 700 F.

or somewhat higher to convert the aluminum salt to the oxide and toconvert the hydrogel into a dry gel. The resulting product is asynthetic impregnated gel of silica and. alumina and may be'used as thebase material for preparing cats:-

5 lysts according to the present invention.

In using these catalysts for the selective removal of acetylene indiolefin-containing hydrocarbon mixtures, the temperature of treatmentmay vary between 50 and 300 0., preferably 50 tol50 C. The feed rate inthe lirlud phase may,

be between about 0.05 and 20 volumes of liquid per volume of catalystper hour, preferably between 0.5 and 5 volumes of liquid per volume ofcatalyst per hour, while the feed'rate inthe About 100 pounds of theground, dried hydrog5 vapor phase may be 0.1 to 2 volumes per volume ofcatalyst per.hour measured as liquid. Pres-' sures may range .iromslightly below atmospheric to slightly above atmospheric. During a theprocess acetylene polymers are formed and are adsorbed on the catalystsupport- It is therewill disolve the polymers or the polymers may beremoved by stripping with oxygen-free steam.

The following examples will further illustrate the invention-but. theinvention is not. to be restricted to the examples which areillustrative Example 1 A hydrocarbon mixture containing butadiene and636 parts per million of C4 acetylenes was passed at a rate of 15 cc.perhour through a 3 it. by 1 in. heat-resistant glass tubecontainperature ranging from 75 to 90 C. This catalyst had beenpreviously reduced with hydrogen. The exit gas from the second houroperation was collected'and the product was shown to contain only 44parts per million of acetylenes.

Example. 2"

- A second run wasmade in the same manner as in Example 1, except thatthe liquid feed was increased to cc. per hour. The product obtainedcontained 228 parts per million of acety- 60 lene, 99.6% of unsaturatedhydrocarbons and 90.6% of butadiene. 4

From the above examples it is evident that the acetylenes weresubstantially completely removed from the butadiene-containing gases.

The nature and objects of the present inven tion having thus been setforth and specific ex-.

arnples of the same given, what is claimed as new and useful and desiredtobe secured by Letters Patent is:

1. A process for selective removal of acetylenes 5 comprising analuminum silicate selected fromthe group consisting ofbentonite andmontmorillonite and which has been previously treated with an acidselected from the group consisting of sulfuric acid, fiuosilicicacid,'and hydrofluoric acid whereby the acetylenes are selectivelypolymerized and withdrawing from the catalyst the diolefinssubstantially free of acetylenes.

2. A process as described in claim '1 in which said catalyst is asulfuric acid-treated bentonite.

3. A process for selective removal of acetylenes from a gaseoushydrocarbon fraction containing diolefins which comprises passing saidgaseous fraction in the absence of hydrogen at a temperature between 50and 300 C. over a catalyst comprising an aluminum silicate selected fromthe group consisting of bentonlte and montmorillonite and which has beenpreviously treated with an acid selectedfrom the group consisting ofsulfuric acid, fluosilicic acid, and hydrofluoric acid whereby theacetylenes are selectively polymerized, withdrawing from the catalystthe said acid-treated aluminum silicate is a sulfuric acid-treatedbentonite.

5. Process according to claim 1 in which the catalyst consists of aminor amount of a group VIII metal and a major amount of saidacidtreated aluminum silicate.

6. Process according to claim 5 in which the catalyst consists of 4 to19% by weight of metallic nickel deposited on bentonite which has beensuccessively treated with sulfuric acid and hydrofluoric acid. EGI V. F'ASCE, By Mrs. Sarah Thomas Fasce, Agent Attorney in Fact.

and

WILLIAM H. WOOD.

REFERENCES CITED The following references are of record in the file ofthis patent:

Frevel Apr. 9, 1946

